The mechanism of DNA replication in bacteriophage lambda will be studied by determining the nucleotide sequence of the replication initiation (ori) site. The replication capacity of lambda will also be exploited as a vehicle for replicating segments of DNA from E. coli, several coli phages, Drosophila and mouse. Additional derivatives of lambda will be constructed with restriction sites for several enzymes optimally located for insertion of foreign DNA. These vectors will be tested for ED2 levels of containment. Selection techniques will be developed for cloning specific eukaryotic genes and for cloning adjacent regions on the eukaryotic chromosome. Clones derived from specific known genes will be studied and nucleotide sequences determined.